Wall surface pressure measurement structure and wind-tunnel test apparatus

ABSTRACT

A wall surface pressure measurement structure measures a wall surface pressure in a duct. Measurement holes are formed in different positions in a circumferential direction on an inspection surface of a wall surface of the duct. The inspection surface is orthogonal to an extending direction of the duct. A pressure chamber communicating with the measurement holes is provided on an outer peripheral side of the duct. The pressure chamber is coupled to a pressure gauge via a pressure pipe.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent ApplicationNo. 2017-207779 filed on Oct. 27, 2017, the entire contents of which arehereby incorporated by reference.

BACKGROUND 1. Technical Field

The present invention relates to a technique that measures an averagevalue of wall surface pressures in a duct.

2. Related Art

A wind-tunnel test for simulating the effect of airflow acting on anaircraft is performed to inspect airflow around a model mimicking theairframe thereof, an aerodynamic force acting on the model, and the like(see, for instance, Japanese Unexamined Patent Application PublicationNo. 10-267786).

When an external load acting on the model is calculated in such awind-tunnel test, the aerodynamic load in an intake duct (air intakeport) due to airflow needs to be removed from the load measurement valueacting on the entire model. The load in the intake duct is calculatedbased on measurement values of the total pressure and a wall surfacepressure in the vicinity of a duct outlet.

An average value on an inspection surface in the vicinity of the ductoutlet is used as this wall surface pressure to take the distribution ina circumferential direction into consideration. Specifically, asillustrated in FIG. 5, a plurality of measurement holes provided in theinspection surface is individually coupled to a pressure gauge viapressure pipes, the pressures in the measurement holes are measured, andthe average value thereof is calculated.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a wall surface pressuremeasurement structure configured to measure a wall surface pressure in aduct. Measurement holes are formed in different positions in acircumferential direction on an inspection surface of a wall surface ofthe duct. The inspection surface is orthogonal to an extending directionof the duct. A pressure chamber communicating with the measurement holesis provided on an outer peripheral side of the duct. The pressurechamber is coupled to a pressure gauge via a pressure pipe.

Another aspect of the present invention provides a wind-tunnel testapparatus including a wind-tunnel; a blower configured to generateairflow in the wind-tunnel; and the wall surface pressure measurementstructure in which the duct is an intake duct provided in a model of anaircraft, and the wall surface pressure in the intake duct of the modelupon receipt of the airflow in the wind-tunnel is measured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic structure of a wind-tunnel test apparatusaccording to an example.

FIG. 2 is a perspective view illustrating a model according to theexample.

FIG. 3 is a longitudinal sectional view illustrating the model accordingto the example taken along an extending direction of an intake duct.

FIG. 4 is a cross sectional view illustrating the intake duct accordingto the example taken along an inspection surface.

FIG. 5 illustrates a wall surface pressure measurement structure ofrelated art.

DETAILED DESCRIPTION

Hereinafter, an example of the present invention will be described withreference to the drawings. Note that the following description isdirected to an illustrative example of the present invention and not tobe construed as limiting to the present invention. Factors including,without limitation, numerical values, shapes, materials, components,positions of the components, and how the components are coupled to eachother are illustrative only and not to be construed as limiting to thepresent invention. Further, elements in the following example which arenot recited in a most-generic independent claim of the present inventionare optional and may be provided on an as-needed basis. The drawings areschematic and are not intended to be drawn to scale. Throughout thepresent specification and the drawings, elements having substantiallythe same function and configuration are denoted with the same referencenumerals to avoid any redundant description.

It is necessary to use as many measurement points (measurement holes) aspossible to more accurately measure and calculate the average value ofwall surface pressures.

However, if the number of measurement points is increased simply, thenumber of pressure pipes is also increased. Then, the measurement valueis affected by the load acting on the pressure pipes, and themeasurement precision is reduced. Therefore, in order to prevent anexcess increase in interference loads due to the pressure pipes, therewas no choice but to keep the number of measurement points small, suchas three. Accordingly, the pressure distribution in a circumferentialdirection may not be measured precisely, and it is difficult to applythe wall surface pressure measurement structure of the related art to astructure in which flow in a duct is complicated.

It is desirable to accurately measure an average value of wall surfacepressures even when flow in the duct is complicated.

FIG. 1 illustrates a schematic structure of a wind-tunnel test apparatus1 according to the example. FIG. 2 is a perspective view illustrating amodel 3 to be installed in the wind-tunnel test apparatus 1. FIG. 3 is alongitudinal sectional view illustrating the model 3 taken along anextending direction of an intake duct 31. FIG. 4 is a cross-sectionalview illustrating an intake duct 31 taken along an inspection surface Swhich will be described later.

As illustrated in FIG. 1, the wind-tunnel test apparatus 1 according tothe example measures an external load and the like acting on anaircraft. The wind-tunnel test apparatus 1 has, in a wind-tunnel 2, themodel 3 mimicking an aircraft and a blower 4 that generates airflow Ffrom the front side of the airframe of the model 3.

The model 3 is attached, via a balance 23, to a tip of a sting 22projecting toward an upstream side in an air blowing direction from asupport member 21 erected on a measurement part in the wind-tunnel 2.

The balance 23 is provided in a fuselage 30 of the model 3 asillustrated in FIG. 2. The balance 23 measures an aerodynamic forceacting on the entire model 3.

The external load acting on the model 3 is calculated by subtracting theaerodynamic load acting on the inside of the intake duct 31 of the model3 from the aerodynamic force acting on the entire model 3 measured bythe balance 23. This is because the aerodynamic load acting on theinside of the intake duct 31 is assumed to be a part of a thrust forcein an actual aircraft.

The aerodynamic load acting on the inside of the intake duct 31 iscalculated based on the total pressure and the wall surface pressure(static pressure) in the vicinity of an outlet of the intake duct 31, asillustrated in FIG. 3. More specifically, the total pressure and thewall surface pressure on the inspection surface S orthogonal to theextending direction of the intake duct 31 are measured and theaerodynamic load is calculated based on these measurement values.

Of these pressures, the total pressure is measured by a pitot tube 24configured to measure multiple points. This pitot tube 24 has tipsinserted into the intake duct 31 from an open rear end so as to belocated on the inspection surface S. The pitot tube 24 is fixed to thesting 22.

On the other hand, the wall surface pressure is measured as an averagevalue of the static pressures in a plurality of (eight in the example)measurement holes 32 formed in the inspection surface S of the wallsurface of the intake duct 31, as illustrated in FIG. 4.

Specifically, the plurality of measurement holes 32 is formed indifferent positions in the circumferential direction at equal intervalsin the circumference on the inspection surface S. All of the pluralityof measurement holes 32 communicates with an annular chamber 33 providedon an outer peripheral side thereof. This chamber 33 is coupled to apressure gauge 26 via a single pressure pipe 25 so that the pressure canbe measured.

This enables the pressure gauge 26 to measure the static pressures inthe plurality of measurement holes 32 averaged in the chamber 33.

As described above, according to the example, the pressures are averagedin the chamber 33 that communicates with the plurality of measurementholes 32 and the averaged pressure is measured by the pressure gauge 26via the pressure pipe 25.

Accordingly, the average value of the wall surface pressures can bemeasured with high precision by directly measuring the averaged wallsurface pressure. In addition, unlike the related-art structure in whichmeasurement holes are coupled to a pressure gauge via separate pressurepipes, the pressure is measured via only the single pressure pipe 25regardless of the number of measurement points (the number of themeasurement holes 32). Therefore, the number of measurement points canbe increased without an increase in interference loads due to thepressure pipe 25.

Accordingly, the average value of the wall surface pressures can beaccurately measured even when flow in the intake duct 31 is complicated.

It should be noted here that examples to which the present invention isapplicable are not limited to the above described example and that theexample can be modified appropriately without departing from the spiritof the invention.

For instance, the chamber 33 is provided in the intake duct 31 in theabove example. However, the structure of the chamber 33 is notparticularly limited to this example as long as the pressures in theplurality of measurement holes 32 can be averaged. For instance, thechamber 33 may be provided separately from the intake duct 31 or mayhave a non-annular shape.

In addition, in the above example, the wall surface pressures of theintake duct 31 in the model 3 of the aircraft are measured by applyingthe wall surface pressure measurement structure according to the exampleof the present invention to the wind-tunnel test apparatus 1. However,the wall surface pressure measurement structure according to the exampleof the present invention is not limited to this measurement instance,but is widely applicable to measurement of a wall surface pressure in aduct.

The invention claimed is:
 1. A wall surface pressure measurementstructure configured to measure a wall surface pressure in a duct,wherein measurement holes are formed in different positions in acircumferential direction on an inspection surface of a wall surface ofthe duct, the inspection surface being orthogonal to an extendingdirection of the duct, a pressure chamber communicating with themeasurement holes is provided between the measurement holes and an outerperipheral side of the duct, and the pressure chamber is coupled to apressure gauge via a pressure pipe.
 2. The wall surface pressuremeasurement structure according to claim 1, wherein the duct is anintake duct provided in a model of an aircraft.
 3. A wind-tunnel testapparatus comprising: a wind-tunnel; a blower configured to generateairflow in the wind-tunnel; and the wall surface pressure measurementstructure according to claim 2, wherein the wall surface pressure in theintake duct of the model upon receipt of the airflow in the wind-tunnelis measured.